Vapor generators of the kind in which a fuel-air mixture is combusted in the direct presense of feed water to produce a useful mixture of steam and non-condensibles are known. See the vaporizers shown in U.S. Pat. No. 3,980,137 and British Pat. No. 283,290. Other similar equipment is shown in: U.S. Pat. Nos. 1,483,917, 2,168,313, 3,563,028, 3,101,592 and 3,449,908.
One difficulty which has been encountered in vaporizers in the past is that of high carbon monoxide content in the product vapor, which is objectionable for many applications and dangerous for some of them. High carbon monoxide production is traceable to incomplete combustion, which is in turn traceable in part to difficulties in maintaining a stable lean flame, and in part to excessive quenching of the flame through direct radiative and convective contact between the flame and the feed water.